The invention relates to a method for the simulation of defects with spark testers, and a spark tester.
As is known, cables and insulated lines must have a predetermined breakdown resistance. For cables and insulated lines, spark tester devices have been available for a long time which test according to various standards the insulation of lines for insulation defects with the aid of a test voltage. There has also been a European standard, EN 50356, the entire contents of which are hereby incorporated by reference, for this purpose for years now, which describes and specifies the design of devices of this type as well as the various test voltages, and furthermore provides instructions on how the sensitivity regarding the recognition of defects in the insulation can be tested. A revised version of the European Standard is EN 62230:2007, the entire contents of which are hereby incorporated by reference. This standard is based on different test voltage forms: alternating voltages of 40 to 62 Hz, alternating voltage with virtually sinusoidal curve and a frequency between 500 Hz and 1 MHz or pulse voltage with a rapid rise and strongly damped fall. A spark tester must furthermore contain a display system that displays defects optically and/or acoustically when the insulation or the jacket of the cable due to faulty insulation or coating does not hold the specific test voltage and a breakdown to the grounded conductor occurs. The defect detector must trigger a digital counter such that each discrete defect is shown. It must also add the defects through to the end of the cable run. The counter must retain the display until the next defect is registered or the display is cleared manually.
For the sensitivity of the spark tester it is required that the defect display is tripped when an artificially generated defect is switched between the electrode and the ground. To this end it is known to provide a so-called defect simulator. It is to be adjusted such that for each simulated defect it generates a discharge in a spark gap of a duration of 0.025 seconds for alternating voltage and high-frequency voltage and of 0.0005 seconds for direct voltage. A sequence of at least 20 discharges of this type is to be triggered, wherein these should not have a time lag of more than one second. The sensitivity of the defect detector is adjusted such that no more and no less than one count pulse per provided discharge is registered.
A known defect simulator, with which the described requirements are met provides an insulation disk, driven by an electric motor via a transmission, which bears an electrode which is permanently at ground potential. A stationary needle electrode is arranged opposite the electrode, which stationary needle electrode is set at the test voltage. The distance between the needle electrode and the disk electrode is predetermined. The dimensions of the needle electrode are also predetermined (Annex B to EN 62230:2007).
The operator of a cable production plant who uses a spark tester device is therefore obligated to test the device from time to time with the aid of a simulator. It is recommended to carry out the assessment of the sensitivity at least once a year, as well as after the first installation and after every repair or major adjustment of the device.
The object of the invention is to disclose a method or a spark tester with which the expenditure for testing for reliability can be substantially reduced.